1. Field of the Invention
The present invention relates to a radio communication system, or more specifically to a communication system comprising a cell site (CS) which is not connected to a switching system and a communication method thereof.
2. Description of the Related Art
Radio communication systems for portable telephones such as cellular systems and cordless telephone systems are known, which comprise a cell site which assigns channels dynamically for connecting a plurality of personal stations (PS) through a radio channel and a line switching network (switching system) for connecting a plurality of cell sites to each other by radio channels or cable lines.
JP-A-6-178345 discloses a technique in which a standby radio channel is provided between CSs, and when a fault occurs in the line between a CS and a switching system, the communication is routed between the CSs through the standby radio channel so that a network and a PS are connected by avoiding the fault point. This technique concerns a method of connecting a PS to a switching system through two CSs, but no method is described for connecting the switching system on the network side to the PS.
A method for an automobile telephone system is described in JP-A-5-68282, wherein in case of a line fault between switching systems, a connection in speech is routed using an adjacent CS, thereby circumscribing the faulty point.
On the other hand, JP-A-4-196626 discloses a technique in which a radio terminal routes signals in a mobile communication system.
These techniques, which provide emergency means in case of a system or line fault, have a limit in the number of applicable connections and applicable status of connection.
In ordinary radio communication systems, installation of a new CS requires the construction of a cable transmission path for connecting the CS to a switching system or the assignment of a new radio frequency band to the CS for connecting the CS and the switching system through a radio channel.
As a result, installation of a new CS is expensive.